| Title of Invention | A BAFFLE PLATE FERMENTOR FOR MANUFACTURING ETHANOL FROM GLUCOSE AND A PROCESS INVOLVING THE SAME |
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| Abstract | A baffle plate fermentor comprising of baffle plates in aqueous phase adapted for the manufacture of ethanol from glucose by subjecting glucose to fermentation in the presence of yeast in a biphasic medium. The organic solvent of the said biphasic medium has high distribution coefficient for ethanol. |
| Full Text | FIELD OF INVENTION The present invention relates to a baffle plate fermentor, and in particular, relates to the fermentor comprising of baffle plates in aqueous phase adapted for the manufacture of ethanol from glucose by subjecting glucose to fermentation in the presence of yeast in a biphasic medium. More particularly, the present invention relates to an improved process for manufacturing ethanol from glucose, facilitated by the use of the said baffle plate fermentor and a suitable organic solvent in the said biphasic medium having high distribution coefficient for ethanol. BACKGROUND ART The conventional way of making ethanol from starch involves either acid or enzymatic hydrolysis followed by fermentation and atmospheric distillation. Anhydrous ethanol is obtained from the ethanol-water azeotrope produced in atmospheric distillation by several ways e.g. using a third component such as benzene to break the azeotrope or using either a membrane or a solid dessicant to remove the water from aqueous ethanol. The conventional processes are both capital and energy intensive. For instance it takes about 24 hours hold up time to complete fermentation of a given batch. Also both capital and energy consumption are high in obtaining anhydrous alcohol using any conventional azeotrope breaking process. Lately, the processes developed are directed to extractive fermentation using a suitable organic solvenc followed by distillation to produce 99.99 % ethanol wherein inert particles of proper shape were employed in the aqueous medium and the fermentor was vibrated to expedite fermentation by increasing the rate of mass transfer in and out of the yeast cells. Faster transfer of alcohol from aqueous to organic phase was achieved by recycling alcohol rich solution from bulk to interfacial region and withdrawal of alcohol depleted liquid from the interface and dispersal into the bulk. The advantages with the abovesaid process rests in cut down of fermentation time, and hence the size of the fermentor, produces 100 % ethanol, and produces the said 100 % ethanol as one of the product using simple technique of extraction of the alcohol into a high boiling organic solvent followed by distillation of the alcohol thereby producing ethanol. Since alcohol is removed into the organic phase as it is produced there is a gradual build up of alcohol in the aqueous phase leading to the higher conversion of glucose. The problem of alcohol inhibition was therefore eliminated in such fermentation processes due to formation of alcohol and simultaneous extraction. The process mainly comprises of simultaneous fermentation and extraction wherein glucose is fermented to ethanol and ethanol is simultaneously extracted out into the organic solvent such as 1- Decanol, Ethyl benzene, Isopropyl benzene, M-ethyl toluene, N-butyl propionate etc. the prerequisites of the said organic solvent being immiscibility with water, has high ethanol solubility and is lighter than the aqueous phase. The quantity of the said organic solvent used depends on a number of factors such as volume of the aqueous phase and distribution coefficient. Since it is the interface through which the alcohol transfer occurs, for faster transfer from the bulk to the interface, the aqueous phase can be pumped out from the bulk and discharge it near the interface continuously during the simultaneous fermentation and extraction process. Thus, maintaining a higher concentration gradient near the interface leads to higher rate of transfer. It is necessary to release the pumped liquid near the interface over the whole area uniformly such that the velocity is reduced as it enters but sufficient to penetrate the whole width of the interface. To enhance the rate of mass transfer appreciably it is suggested that not only one should recycle the alcohol rich liquid from the bulk to the interfacial region but also withdraw alcohol depleted layer (which sinks from the interface) from the interface where alcohol concentration is low and discharge below it in the bulk of the phase uniformly such that the concentration of alcohol in the bulk reduces uniformly. Essentially, what is achieved is faster rate of mass transfer by forced recycle and forced withdrawal that is faster than the natural convection currents. The rate of transfer of the alcohol rich liquid from the bulk can be varied by means of a valve and the rate of withdrawal of alcohol depleted liquid can also be controlled by means of a valve. Both these rates should be optimized such that the rate of decrease of alcohol concentration in the bulk matches the rates of transfer across the interface and that from the interface to the organic phase. As already discussed above the fermentation process can be further expedited by shaking the fermentor and adding a iarge number of inert particles of appropriate shape and size in the aqueous phase. As the vessel is moved back and forth, the liquid adjacent to the vessel wall moves and portion of it pushes the particle while the other portion passes through the gap. Thus there occurs a velocity gradient in the gap because the particle moves at a slower velocity due to its weight than the liquid through the gap. Due to this velocity gradient within the liquid body, mass transfer rates in and out of the yeast cells increase by different amounts in the liquid layers which otherwise will not happen in absence of the particles and the said back and forth movement. At the end of the fermentation and extraction process the organic phase is pumped to a distillation column for separating 100 % ethanol from the organic solvent which is recycled. The aqueous phase containing ethanol, yeast, water and unconverted glucose is pumped to a distillation column after solid separation wherein alcohol is separated out as 95.6 % ethanol at the top and the bottom is waste water which can be either biodegraded or incinerated. Further modification to the above process in Indian patent no. 201474 by Dr. A. Sirkar was based on recycling techniques of the organic phase in addition to the already existing recycling of the aqueous phase, vibrating the fermenting vessel packed with inert particles to increase the rate of production. The reason behind such a modification is to recover maximum amount of alcohol from glucose in the shortest possible time and it was also observed in the said improved process that the rate of transfer of alcohol from the aqueous phase to the organic phase is affected by concentration factors of alcohol in the organic phase. The process mainly comprises of simultaneous fermentation and extraction wherein glucose is fermented to ethanol and ethanol is simultaneously extracted out into the organic solvent such as 1- Decanol, Ethyl benzene, Isopropyl benzene, M-ethyl toluene, N-butyl propionate etc. Amongst these solvents the desirable ones are those for which the distribution coefficient, which is the concentration ratio of alcohol between the organic phase and aqueous phase, are high, in addition to the high boiling point such that substantial amount of alcohol can be extracted into the organic phase and separation of alcohol from the organic solvent would be easier with less capital investment and lower operating cost. It is thus clearly apparent form the abovesaid discussions that there is a long felt need in the art to provide for improvements in the existing process for the manufacture of ethanol from glucose involving fermentation of glucose by yeast that would thereby lead to a cost-effective process and would further assist to curtail the fermentation time required to ferment glucose along with the size of the fermentor. OBJECTS OF THE INVENTION It is thus the basic object of the present invention to provide for baffle plate fermentor for the manufacture of ethanol from glucose by subjecting glucose to fermentation in the presence of yeast in a biphasic medium which would avoid the limitations of the known prior art processes employing a solvent with low distribution coefficient and flat particles (with gaps inside) which require regular stacking to be effective as otherwise the same leads to not only poor extraction of the produced ethanol in the said solvent in the said fermentor or vessel but also lower the rate of fermentation in the aqueous phase. Another object of the present invention is to provide for a suitable organic solvent in the said biphasic medium into which ethanol is extracted after being produced from fermented glucose in aqueous medium with high distribution coefficient for ethanol. Yet another object of the present invention is to provide for improvements in the existing process for the manufacture of ethanol from glucose involving fermentation of glucose by yeast that would lead to a cost-effective process by employing the said fermentor of the invention which would further assist to curtail the fermentation time required to ferment glucose and the size of the fermentor. SUMMARY OF THE INVENTION Thus according to the basic aspect of the invention there is provided a Baffle plate fermentor adapted for reduced fermentation time for the manufacture of ethanol from glucose in a biphasic medium with an aqueous phase below an organic phase comprising: means adapted for back and forth movement of said fermentor; baffle plates installed vertically that are parallel to the walls of fermentor in the said aqueous phase to favour the formation of the said velocity gradient in the boundary layer of the said aqueous phase next to the plates due to the said back and forth movement of the said fermentor thereby adapted to increased rates of mass transfer from bulk to ceil wall of glucose and from cell wall to bulk of alcohol whereby the flocs are subjected to lateral velocity to favour the mass transfer rate and reduce the fermentation time. In another preferred aspect of the invention there is provided a Baffle plate fermentor wherein said fermentor is adapted for higher velocity of said back and forth movement of the said fermentor to facilitate higher velocities of different layers within the boundary layer of the aqueous phase next to the said baffle plates thereby facilitating said higher mass transfer rates as compared to a stagnant system. In yet another aspect of the invention there is provided a process for the manufacture of ethanol from glucose comprising subjecting glucose to fermentation in the presence of yeast in a fermentor and in a biphasic medium comprising the steps of subjecting an aqueous solution of glucose to fermentation in the presence of yeast and ethyl oleate as an organic solvent of the said biphase such as to attain favourable distribution coefficient of ethanol in said organic solvent and obtain an aqueous phase containing a product of fermentation and an organic phase above the aqueous phase having high purity ethanol that is transferred to the organic phase from the aqueous phase due to the said high distribution coefficient of ethanol in the said organic solvent. In another aspect of the invention there is provided a process for the manufacture of ethanol from glucose wherein said fermentor used comprises a baffle plate fermentor with the baffle plates installed vertically that are parallel to the walls of fermentor in the said aqueous phase to favour the formation of the said velocity gradient in the boundary layer of the said aqueous phase next to the plates due to the said back and forth movement of the said fermentor thereby adapted to increased rates of mass transfer from bulk to cell wall of glucose and from cell wall to bulk of alcohol whereby the flocs are subjected to lateral velocity to favour the mass transfer rate and reduce the fermentation time. In accordance with a preferred aspect of the invention there is provided a process for the manufacture of ethanol from glucose wherein the aqueous phase at the lower level of the fermentor is recirculated in the process in the following manner: a) withdrawing a stream of the aqueous phase from the intermediate location in the aqueous phase and recirculate the same to the aqueous phase at a level below that of the interface of the aqueous phase and organic phase; b) withdrawing a stream of the aqueous phase from a level immediately adjacent to interface from a location which is above the location of the admitted stream (a) above and recirculating the said withdrawn stream to a lower level in the aqueous phase; c) withdrawing the product stream from near the bottom of the aqueous phase; d) subjecting the said stream to centrifug3tion to separate spent yeast and useful liquid stream; e) Recirculate the recovered yeast and subjecting the useful liquid stream to distillation to obtain ethanol stream (95.6 % pure) and waste water effluent stream and wherein the organic phase at the top level of the biphase is subjected to recirculation in the following manner; a) withdrawing the organic stream containing alcohol from near and above the interface and recirculate same to the bulk of the organic phase at a higher level; b) withdrawing the stream organic phase from the bulk region and recirculating the same at near the interface; c) withdrawing the product stream from the organic phase at a level from just above the interface containing high purity alcohol; d) Subjecting the above stream to distillation to separate the organic solvent and the alcohol recycling the recovered solvent to the fermentor and recovering alcohol as the final product from the final product stream having 100 % ethanol. In accordance with yet another preferred aspect of the invention there is provided a process wherein the fermentor comprising the baffle plates in the aqueous phase is subjected to mechanical vibration so as to move back and forth facilitating the creation of a velocity gradient in the boundary layer of the aqueous phase next to the said plates characterized in that the higher velocity of back and forth movement facilitates higher velocities of different layers within the boundary layer and thus higher mass transfer from bulk to cell wall of glucose and from cell wall to bulk of alcohol. BRIEF DESCRIPTION OF FIGURES Figure 1: illustrates the baffle plate fermentor (1) with circulations in both the aqueous and the organic phase in the form of a flow diagram to be used for fermentation; Figure 2: illustrates the top view of the baffle plate fermentor with incorporated baffle plates. The details of the invention, its objects and advantages are explained here under in greater details in relation to non-limiting exemplary illustrations as per the following drawings. DETAILED DESCRIPTION OF THE INVENT ION As described hereinbefore, there is provided a baffle plate fermentor adapted to manufacture ethanol from glucose comprising subjecting an aqueous solution of around 10 percent glucose concentration and fermented at around 30 °C in the presence of yeast followed by separating ethanol produced at a pH of 4.5 and wherein the fermentation is carried out in the presence of organic solvent with high distribution coefficient such as ethyl oleate so as to obtain an organic phase having high purity ethanol obtained from fermentation and wherein the organic phase and the aqueous phase are maintained in the volume ratio of 1:1, further subjecting the aqueous phase at the lower level of the biphase to recirculate in the following manner: a) withdrawing a stream of the aqueous phase from the intermediate location in the aqueous phase and recirculate same to the aqueous phase at a level below that of the interface of aqueous phase and organic phase; b) withdraw the stream of aqueous phase from the level immediately adjacent to interface from a location which is above the location at which the first mentioned recirculated stream is admitted as mentioned under point (a) above and recirculating the said withdrawn stream to a lower level in the aqueous phase; c) withdrawing the product stream from near the bottom of the aqueous phase; d) subjecting the said stream to centrifugation to separate spent yeast and useful liquid stream; e) Recirculate the recovered yeast and subjecting the useful liquid stream to distillation to obtain ethanol stream (95.6 percent pure) and waste water effluent stream and wherein the organic phase at the top level of the biphase is subjected to recirculation in the following manner; a) withdrawing the organic stream containing alcohol from near and above the interface and recirculate same to the bulk of the organic phase at a higher level; b) withdrawing the stream organic phase from the bulk region and recirculating the same at near the interface; c) withdrawing the product stream from the organic phase at a level from just above the interface containing high purity alcohol; d) Subjecting the above stream to distillation to separate the organic solvent and the alcohol recycling the recovered solvent to the fermentor and recovering alcohol as the final product from the final product stream having 100 percent ethanol. It is seen form the flow diagram in Figure 1 that a fermentor (1) with baffle plates (BP) is used in which the fermentation of the required liquid takes place. An aqueous phase (2) is obtained which stays at the lower portion of the fermentor as aqueous phase and wherein the organic and the aqueous phase is divided by an interface (I). An organic solvent is used to extract the alcohol produced due to fermentation and this produces an upper organic phase (3). The liquid slightly below the interface is recycled (4) to the aqueous phase. From an intermediate location in the aqueous phase, a stream (7) is withdrawn and recycled as stream (6) just below the level of withdrawal of (4). A stream (5) having alcohol is withdrawn from the bottom of the aqueous phase and is pumped to a centrifuge (8). In the centrifuge the spent yeast is separated from the liquid phase (9) having the alcohol. The liquid phase (9) is subjected to distillation in the distillation column (10) to obtain the distilled alcohol phase (11) of 95.6 % strength and a waste water stream (12) is sent to the effluent treatment plant. The organic phase containing the alcohol is also subjected to recycling in a manner similar to the aqueous phase. The liquid in the organic phase (3) from the bulk is recycled to a lower level as stream 4-A. A stream 6-A is withdrawn from below the level of injection of stream 4-A adjacent to the interface and injected in the bulk of the organic phase. Further a stream 5A having pure alcohol (99.9 %) is withdrawn from the bottom of the organic phase as stream (13) and is subjected to the distillation unit (14) for the separation of solvent and alcohol. The distilled alcohol stream is 100 % pure ethanol wherein the solvent stream is further sent to the fermentor. The finely divided inert particles used in prior fermentation processes were substituted by the baffle plate (BP) fermentor by way of the present invention that provides for an improved technique for cutting down the fermentation time as illustrated in (Figure 2) representing the top view of the baffle plate fermentor with incorporated baffle plates. The fermentor consists of baffle plates installed vertically (parallel to the wall of fermentor) in the aqueous phase. When the fermentor moves the liquid inside the vessel moves and creates a velocity gradient in the boundary layer next to the plates. This velocity gradient is responsible for increased rates of mass transfer from bulk containing glucose to cell walls of yeast and from cell wall of yeast to bulk of alcohol thus, cutting down the fermentation time. With higher velocities of back and forth movement, higher are the velocities of different layers within the boundary layer and since the flocs are subjected to lateral velocity, mass transfer rates are higher compared to stagnant system. The invention is explained in further details by way of the following non-limiting examples: Example-I: Process and process parameters for the conversion of Glucose to alcohol 20 liters of Molasses diluted to 10 % fermentable sugar (which is glucose), specific gravity 1.08 and 20 liters of solvent ethyl oleate were subjected to fermentation at around 30 °C in the presence of yeast for about 2.0 hours. The conversion of glucose to alcohol achieved was 90%. Recycle rates were 4 litres/hr, for two recycles in the aqueous phase and 2 litres/fr for two recycles in the organic phase. Time of fermentation in the aqueous phase and simultaneous extraction into the organic phase was 2 hours. The amount of total ethanol produced at the end of the fermentation was found to be 0.9568 kg of alcohol in 2 hours. This total amount of alcohol was the amount present in the upper organic phase as 100 % ethanol and in the lower aqueous phase as 95.6 % ethanol. The amount of ethanol in the organic phase (20 litres) was about 0.6834 kg. The amount of ethanol in the aqueous phase was about 0.2734 Kg. Further the correctness in the actual amount of ethanol produced was further confirmed and verified form the distribution coefficient of the said organic solvent and water in use of the aforesaid fermentation process, the calculations for which are presented below: Aqueous phase volume = 20 litres Organic phase volume = 20 litres Initial Glucose Concentration in Aqueous phase = 10 % by volume (sp.gr.-1.04) Glucose conversion Achieved = 90% Total alcohol produced = 0.9568 kg .-.0.9568 = cw x 20 + csol x 20 where cw & csol are final concentration of ethanol in aqueous and solvent phase respectively. The total amount of absolute alcohol thus produced in the organic phase = 0.6834 kg in 20 litres of solvent (0.01367 kg/lit x 20 lit = 0.6834 kg) This is equivalent to 71.4% (0.6834 kg / 0.9568 kg x 100) of the total alcohol produced that is 100% pure. It is thus possible by way of the present invention to provide for a superior fermentation technique by way of employing the baffle plate fermentor with baffle plates installed vertically in the aqueous phase of the biphase facilitating the fermentation process by creating a velocity gradient in the boundary aqueous layer next to the plates due to the back and forth movement of the fermentor thereby leading to increased rates of mass transfer from bulk containing glucose to cell walls of yeast and from cell wall of yeast to bulk of alcohol thus, cutting down the fermentation time. The process of the present invention is thus cost-effective in achieving higher yield of 100 % ethanol in reduced fermentation time and also helps in curtailing the size of the fermentor to achieve the same higher yield of ethanol. We Claim: 1. A Baffle plate fermentor adapted for reduced fermentation time for the manufacture of ethanol from glucose in a biphasic medium with an aqueous phase below an organic phase comprising: means adapted for back and forth movement of said fermentor; baffle plates installed vertically that are parallel to the walls of fermentor in the said aqueous phase to favour the formation of the said velocity gradient in the boundary layer of the said aqueous phase next to the plates due to the said back and forth movement of the said fermentor thereby adapted to increased rates of mass transfer from bulk to cell wall of glucose and from cell wall to bulk of alcohol whereby the flocs are subjected to lateral velocity to favour the mass transfer rate and reduce the fermentation time. 2. Baffle plate fermentor as claimed in claim 1 wherein said fermentor is adapted for higher velocity of said back and forth movement of the said fermentor to facilitate higher velocities of different layers within the boundary layer of the aqueous phase next to the said baffle plates thereby facilitating said higher mass transfer rates as compared to a stagnant system. 3. A process for the manufacture of ethanol from glucose comprising subjecting glucose to fermentation in the presence of yeast in a fermentor and in a biphasic medium comprising the steps of subjecting an aqueous solution of glucose to fermentation in the presence of yeast and ethyl oleate as an organic solvent of the said biphase such as to attain favourable distribution coefficient of ethanol in said organic solvent and obtain an aqueous phase containing a product of fermentation and an organic phase above the aqueous phase having high purity ethanol that is transferred to the organic phase from the aqueous phase due to the said high distribution coefficient of ethanol in the said organic solvent. 4. A process for the manufacture of ethanol from glucose as claimed in claim 3 wherein said fermentor used comprises a baffle plate fermentor with the baffle plates installed vertically that are parallel to the walls of fermentor in the said aqueous phase to favour the formation of the said velocity gradient in the boundary layer of the said aqueous phase next to the plates due to the said back and forth movement of the said fermentor thereby adapted to increased rates of mass transfer from bulk to cell wall of glucose and from cell wall to bulk of alcohol whereby the flocs are subjected to lateral velocity to favour the mass transfer rate and reduce the fermentation time. 5. A process for the manufacture of ethanol from glucose as claimed in anyone of claims 3 or 4 wherein the aqueous phase at the lower level of the fermentor is recirculated in the process in the following manner: a) withdrawing a stream of the aqueous phase from the intermediate location in the aqueous phase and recirculate the same to the aqueous phase at a level below that of the interface of the aqueous phase and organic phase; b) withdrawing a stream of the aqueous phase from a level immediately adjacent to interface from a location which is above the location of the admitted stream (a) above and recirculating the said withdrawn stream to a lower level in the aqueous phase; c) withdrawing the product stream from near the bottom of the aqueous phase; d) subjecting the said stream to centrifugation to separate spent yeast and useful liquid stream; e) Recirculate the recovered yeast and subjecting the useful liquid stream to distillation to obtain ethanol stream (95.6 % pure) and waste water effluent stream and wherein the organic phase at the top level of the biphase is subjected to recirculation in the following manner; a) withdrawing the organic stream containing alcohol from near and above the interface and recirculate same to the bulk of the organic phase at a higher level; b) withdrawing the stream organic phase from the bulk region and recirculating the same at near the interface; c) withdrawing the product stream from the organic phase at a level from just above the interface containing high purity alcohol; d) Subjecting the above stream to distillation to separate the organic solvent and the alcohol recycling the recovered solvent to the fermentor and recovering alcohol as the final product from the final product stream having 100 % ethanol. 6. Process as claimed in anyone of claims 4 or 5 wherein the fermentor comprising the baffle plates in the aqueous phase is subjected to mechanical vibration so as to move back and forth facilitating the creation of a velocity gradient in the boundary layer of the aqueous phase next to the said plates characterized in that the higher velocity of back and forth movement facilitates higher velocities of different layers within the boundary layer and thus higher mass transfer from bulk to cell wall of glucose and from cell wall to bulk of alcohol. 7. A fermentor comprising baffle plates in aqueous phase for the manufacture of ethanol from glucose by subjecting glucose to fermentation in the presence of yeast in a biphasic medium and a process thereof substantially as herein described and illustrated with reference to the accompanying drawings. A baffle plate fermentor comprising of baffle plates in aqueous phase adapted for the manufacture of ethanol from glucose by subjecting glucose to fermentation in the presence of yeast in a biphasic medium. The organic solvent of the said biphasic medium has high distribution coefficient for ethanol. |
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| Patent Number | 278004 | ||||||||||||
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| Indian Patent Application Number | 127/KOL/2010 | ||||||||||||
| PG Journal Number | 51/2016 | ||||||||||||
| Publication Date | 09-Dec-2016 | ||||||||||||
| Grant Date | 08-Dec-2016 | ||||||||||||
| Date of Filing | 11-Feb-2010 | ||||||||||||
| Name of Patentee | ROY, SEBAK RANJAN | ||||||||||||
| Applicant Address | 656/3 ASHOK NAGAR, P.O. ASHOK NAGAR, DIST, NORTH 24 PARAGANAS, WEST BENGAL 743222, INDIA | ||||||||||||
Inventors:
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| PCT International Classification Number | C12P7/06 | ||||||||||||
| PCT International Application Number | N/A | ||||||||||||
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